Process for controlling a start-stop operation of a vehicle having a hybrid drive, and a corresponding vehicle

ABSTRACT

A process for controlling a vehicle start-stop operation having a hybrid drive with an internal-combustion engine and an electric motor, a service brake with an ABS and an electric parking brake, includes: determining, monitoring and analyzing performance parameters of the vehicle, the internal-combustion engine, the electric motor, the service brake and the parking brake; automatically releasing the parking brake in the case of a starting prompt because of determined performance parameters; driving the vehicle by the electric motor for the start; starting the engine by the electric motor if the engine is switched off; driving the vehicle by the electric motor and the engine; activating a generator operation of the electric motor in the case of a braking prompt because of determined performance parameters; activating the service brake; and automatically locking the electric parking brake when the vehicle is stopped after a previously definable deceleration time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 12/683,749, filedJan. 7, 2010, which claims priority under 35 U.S.C. §119 to GermanPatent Application No. DE 10 2009 004 023.4, filed Jan. 8, 2009, theentire disclosures of which are herein expressly incorporated byreference.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a process for controlling a start-stopoperation of a vehicle having a hybrid drive, as well as to a vehiclewhich can carry out the process.

Vehicles having a hybrid drive, for example, with an internal-combustionengine as a gasoline, gas or diesel engine, and an electric motor as asynchronous motor, are known in various designs, such as parallelhybrids and series hybrids and include service brake systems with anABS.

A start-stop operation of a vehicle, particularly in city traffic, forexample, at traffic lights or in a traffic jam, necessitates asuccessive starting and decelerating of the vehicle. During stoppagetimes of the vehicle, the engine, i.e., the internal-combustion engine,is switched off in order to save fuel and to reduce pollutant emissions.When starting, the internal-combustion engine will then be started andthe vehicle will be accelerated until the next deceleration. Start-stopsystems for motor vehicles are known in which operating conditions ofthe vehicle and of the operating pedals are determined and are analyzedfor switching off and restarting the internal-combustion engine. Thisapplies especially to vehicles in stop-and-go traffic and particularlyto supply and delivery driving, such as mail and parcel services usingmedium-sized vehicles, in which case a parking brake has to be operatedwhen stopping and has to be released when starting. As a result of thefrequent torque—load change in the transmission line, whereby theinternal-combustion engine is operated outside its ideal characteristicdiagram, high wear, high fuel consumption, as well as a constantuncomfortable operation of the parking brake should be considered to bedisadvantages.

It is therefore an object of the present invention to create an improvedprocess for controlling a start-stop operation of a vehicle having ahybrid drive, whereby the above-mentioned disadvantages will beeliminated or considerably reduced and additional advantages will beprovided. A further object consists of providing a correspondingvehicle.

According to the present invention, a process is provided forcontrolling a start-stop operation of a vehicle, which has a hybriddrive with an internal-combustion engine and an electric motor, aservice brake with an ABS, and an electric parking brake. The processincludes the following steps: (S1) determining, monitoring and analyzingperformance parameters of the vehicle, of the internal-combustionengine, of the electric motor, of the service brake and of the electricparking brake, the performance parameters featuring the vehicle speed,the rotational wheel speed, the rotational speeds of theinternal-combustion engine and of the electric motor, operations andconditions of a service brake pedal, of a parking brake pedal and of anaccelerator pedal; (S2) automatically releasing the electric parkingbrake in the case of a starting prompt because of determined performanceparameters; (S3) driving the vehicle by way of the electric motor forthe start; (S4) starting the internal-combustion engine by way of theelectric motor if the internal-combustion engine is switched off; (S5)driving the vehicle by way of the electric motor and theinternal-combustion engine; (S6) activating a generator operation of theelectric motor in the case of a braking prompt because of determinedperformance parameters; (S7) activating the service brake; and (S8)automatically locking the electric parking brake when the vehicle isstopped after a previously definable deceleration time.

A corresponding vehicle having a hybrid drive with aninternal-combustion engine and an electric motor has the following: aservice brake with an ABS control unit and a service brake pedal; anelectric parking brake with a parking brake control and a parking brakelever; at least one clutch for coupling the internal-combustion engineand the electric motor with the wheels of the vehicle; a hybrid drivecontrol unit for controlling the hybrid drive; and a bus for connectingcontrol units, actuators and sensors of the vehicle and the transmissionof control signals. The electric parking brake is connected with thehybrid drive control unit for an automatic controllability in previouslydefinable operating conditions of the vehicle.

As a result of the automatic controllability of the electric servicebrake when controlling the start-stop operation of a vehicle with asimultaneously adapted control and utilization of the electric motor, itbecomes possible to advantageously simplify a starting operation and astopping operation for the driver in that the operating comfort isincreased and the driver's attention is not diverted from the trafficwhen he leaves the vehicle and starts to drive. In this case, fuelconsumption is reduced because the electric motor carries out thestarting operation and/or assists the internal-combustion engine.

A start or starting prompt when the vehicle is stopped can be determinedby the fact that the brake pedal is released or the parking brake waspreviously locked and the accelerator pedal is operated, which may, forexample, be so in the case of a stop at a traffic light. When thevehicle is stopped, after entering the vehicle, the operation of astarting button or an ignition lock while the accelerator pedal issimultaneously operated may represent a starting prompt. Additionalcombinations are contemplated.

In the case of a driving vehicle, a braking prompt is generated byoperating the service brake pedal or by a corresponding signal of aso-called braking assistant.

In the case of a stop or halt operation, another advantage consists ofthe fact that the electric motor or the hybrid drive is additionallyused as a brake in the event of a braking prompt, a transition takingplace for using the service brake. In this case, the electric motor, asa generator, can take over a braking function of the vehicle and cansimultaneously convert the braking power to electric power for charginga vehicle battery.

As a result of the detection of performance parameters, it becomespossible to determine whether, after a stopping operation, the vehiclecontinues to be stopped, in which case, the parking brake will then belocked automatically, which, in turn, represents an operating comfortfor the driver and offers additional safety because the parking brakemay often be forgotten.

The automatic releasing of the electric parking brake and the driving ofthe vehicle by means of the electric motor can be carried outsimultaneously. This can also increase the operating comfort,particularly in the case of vehicles with a manual transmission, becauseconcentrating on releasing the parking brake and simultaneously startingwithout having the vehicle roll backwards can be eliminated whenstarting on a slope.

When the internal-combustion engine is switched off while the vehicle isstopped, a starting of the internal-combustion engine can take placeafter the expiration of a previously definable time period after theprocess step of driving the vehicle by using the electric motor. Whenthe internal-combustion engine is still in operation, the electric motorcan assist the starting operation, in which case the internal-combustionengine is assisted in such a manner that its efficiency is as high aspossible and the fuel consumption is low.

When a braking prompt occurs, the generator operation of the electricmotor and the service brake can be activated simultaneously. As analternative, it is also contemplated that the process step of activatingthe service brake takes place after the expiration of a previouslydefinable time period after the activating of the generator operation ofthe electric motor.

It is a special advantage that, when a circuit defect of the servicebrake is determined in the process step of determining, monitoring andanalyzing performance parameters and, while the vehicle is driving, abraking prompt is made by means of the service brake pedal and/or theparking brake lever, the process also features the following processsteps for an emergency running function, which is also called “secondarybraking I”: (S1.A1) activating a generator operation of the electricmotor; (S1.A2) activating the electric parking brake; and (S1.A3)automatically locking the electric parking brake when the vehicle isstopped after a previously definable deceleration time. Also in the caseof a defective service brake pedal, an emergency running function(“secondary braking II”) is contemplated, in which case the followingprocess steps take place: (S1.B1) activating operable electric modulesof a control unit ABS of the service brake; (S1.B2) activating agenerator operation of the electric motor; (S1.B3) activating theelectric parking brake; and automatically locking the electric parkingbrake when the vehicle is stopped after a previously definable delaytime.

The operable electric modules may have a reservoir connection forcompressed brake control air or compressed brake control operating air,which can be used for an electromechanical controlling of the servicebrake.

The activation of the generator operation of the electric motor mayfeature a step-by-step adjusting of the generator operation. Within therange of the stepping capability, a PWM triggering of an actuator systemof the parking brake can take place. This actuator system may have aspring-type servo-cylinder (pneumatic or hydraulic in the case of AOH,i.e. air over hydraulic) or may have electromotive or electromechanicalapplication devices.

In one embodiment, the parking brake is adjusted in steps in previouslydefinable ranges during the process step of activating the electricparking brake. It is also contemplated that, by means of the performanceparameters determined in the process step of the determining, monitoringand analyzing of performance parameters, a corresponding assist torqueof the electric motor is calculated for assisting or implementing thestepped ranges of the parking brake. This calculation can, for example,take place in a hybrid drive control unit or in an electric motorcontrol unit.

In addition, the electric parking brake is constructed such that it hasa bistable behavior in the parked condition, whereby, when the electricsupply fails, the electric parking brake is locked or releasedcorresponding to a predetermination by the hybrid drive control unit,another assigned control device, or a driver's intention.

In the case of a trailer operation, a braking system of at least onetrailer of the vehicle can be synchronously activated in the event of abraking prompt.

The previously definable operating conditions of the vehicle may, forexample, be a start-stop operation, an emergency running function in thecase of a circuit defect of the service brake and/or an emergencyrunning function in the case of a defective service brake pedal.

In a preferred embodiment, the internal-combustion engine is constructedas a diesel engine.

The electric motor may be arranged in a parallel or serial position withrespect to the internal-combustion engine. The performance parametersvehicle speed, wheel speed, status of the service and parking brake,data of the electric motor control unit and of the internal-combustionengine control unit are monitored, determined and analyzed. These dataare, for example, available on a bus, such as a CAN bus.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of one ormore preferred embodiments when considered in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an embodiment of a vehicle according tothe invention;

FIG. 2 is a schematic graphic representation of an ideal minimalconsumption;

FIG. 3 is a schematic graphic representation of a start-stop operation;and

FIG. 4 is a flowchart illustrating an exemplary process for controllinga start-stop operation of a vehicle according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Identical constructional elements or functional units with the samefunction have the same reference numbers in the figures.

FIG. 1 schematically illustrates an embodiment of a vehicle 1 accordingto the invention. Functional units of the vehicle 1 are shown as blocksin the manner of an energy and signal flow chart. In this case, solidlines with arrows represent energy fluxes and broken lines representsignal flows.

The vehicle 1 has a serial hybrid drive. An internal-combustion engine2, preferably a diesel engine, is coupled with an electric motor 3 byway of a clutch 4. The electric motor 3 is connected by way of a furtherclutch 4′ with a transmission 5, for example, a transfer transmission,with wheels 6 of the vehicle 1 by way of a transmission line.Furthermore, the electric motor 3 is coupled with a battery 7 as a powersource. The battery 7 may, for example, be a high capacity batteryand/or a fuel cell. The wheels 6 are equipped with a service brake 8 anda parking brake 10.

Between the internal-combustion engine 2, the clutch 4 and the electricmotor 3, an energy flux is illustrated in solid lines as a drivingtorque 21, which is generated by the internal-combustion engine and isfurther transmitted by way of the clutch 4′ and the transmission 5 tothe wheels 6. A driving torque 21′ of the electric motor 3 is guided byway of the clutch 4′ to the transmission line by way of the transmission5 to the wheels 6. The battery 7 supplies a driving current 32 for theelectric motor 3. By way of the clutch 4, the electric motor 2 canfurthermore admit a starting torque 22 to the internal-combustion engine2 in order to start the latter.

During a braking operation, the service brake 8 absorbs a servicebraking torque 23 and the parking brake 10 absorbs a parking braketorque 24. By way of the transmission line, the rotating wheels 6 in thecoasting operation transmit a generator torque 25 to the electric motor3 which, in this case, operates as a generator and converts thegenerator torque 25 to electric power, by which, for example, thebattery 7 is charged by a charging current 31. The generator torque 25can also be transmitted to the internal-combustion engine 2 when theclutch 4 is engaged. Then, the internal-combustion 2 will act as anengine brake, or its possible engine brake units (not shown) connectedwith the internal-combustion engine 2 can be acted upon in this mannerby the generator torque 25 in order to additionally indirectly brake thewheels 6.

The internal-combustion engine 2 is connected with aninternal-combustion engine control unit 15 by way of a signal line. Thiscontrol unit 15 is established for known control purposes of aninternal-combustion engine and will not be further discussed in detail.An electric motor control unit 16 is connected with the electric motor 3and controls the latter as an electric motor and as a generator forcharging the battery 7. In this example, the electric motor control unit16 is simultaneously also responsible for monitoring the battery.

The service brake 8 is linked with an ABS control unit 14 having an ABSfunction, which will also not be explained in detail, and with a servicebrake pedal 9 for the braking prompt. The electric parking brake 10 hasan actuator 34 which can be applied, for example, as a spring-typeservo-cylinder (pneumatically or hydraulically in the case of AOH) orelectromotively or electromechanically. The parking brake 10 iscontrolled by a parking brake control 13 which is coupled with a parkingbrake lever 11 for the manual operation. In this case, the parking brake10 can be controlled in previously adjustable steps. Within the range ofthis stepping capability, the actuator 34, for example, a motor orcylinder, can be triggered by means of a pulse width modulation (PWM).Furthermore, the actuator 34 has a bistable course of action. This meansthat its effect on the brake lining of the service brake is such that,when the electric power source is switched off, the brake remains in anapplied or released position, as previously defined by the system, i.e.by the parking brake control 13 or a higher-ranking control (see below)or a driver's intention.

These control units 15, 16, 13 and 14 as well as controls (not shown indetail) of the clutches 4, 4′, which, for example, areelectromagnetically controllable clutches, and a trailer control valve19 are connected with a bus 17, such as a CAN bus, to which a hybriddrive control unit 12 is connected. The bus 17 is connected with atrailer bus 18 by way of a trailer interface 20.

In this example, the hybrid drive control unit 12 has software forcontrolling the hybrid drive including a higher-ranking control of thebrakes. It thereby becomes possible to advantageously achieve a linkingof the hybrid drive with an automatic release and locking of the parkingbrake 10 for certain operating conditions of the vehicle. It therebybecomes possible to control a start-stop operation SSB, which, asillustrated by FIG. 2 in a schematic graphic representation of an idealminimal consumption MW, is situated in an area outside the idealcharacteristic diagram of the hybrid drive, such that the electric motor3 assists the internal-combustion engine 2, preferably a diesel engine,so that the latter operates with an ideal efficiency.

In FIG. 2, a torque is entered above a rotational speed, an arrowindicating a boosting performance 26 that is required for increasing thetorque, for example, by the internal-combustion engine 2 or additionallyby the electric motor 3. Furthermore, a storage capacity 27 is indicatedby a downward-pointing arrow, which, during a braking operation, can beconverted by the electric motor 3 from a torque to an electric current,which then results in a storage of electric power in the battery 7.Status values of the internal-combustion engine control unit 15 aredetermined together with the vehicle speed as performance parameters ofthe vehicle 1 and are analyzed, for example, also evaluated with respectto time. Simultaneously, data from a central onboard computer (ZBR) or avehicle controlling computer (FFR), such as braking activities of theservice brake pedal 9, are present on the bus 17. From these performanceparameters, an assist torque, for example, is computed by the hybriddrive control unit 12 for the electric motor 3 in order to assist theinternal-combustion engine 2 with respect to its ideal efficiency.

Performance parameters of the vehicle, of the internal-combustionengine, of the electric motor, of the service brake, and of the electricparking brake are, for example, the following: vehicle speed, wheelspeed, rotational speeds of the internal-combustion engine and of theelectric motor, operations and conditions of a service brake pedal, of aparking brake lever and of an accelerator pedal. These can be retrievedfrom corresponding sensors or pertaining controls or a central computerand/or bus system.

As illustrated in FIG. 1, the hybrid drive is capable of uncoupling theinternal-combustion engine 2 from the transmission line by means of theclutches 4, 4′ and to carry out the driving torque 21′ for the wheels 6by the electric motor 2. In the start-stop range or start-stopoperation, by way of the hybrid drive control unit 12, the start-stopfunction is linked with the electric parking brake 10. This means, inother words: by operating the service brake pedal 9, the electric motor3 is switched by its control unit 16 to the generator operation, inwhich case the generator torque 25 generated by the wheels 6 in thecoasting operation drives the electric motor 3. This takes place beforethe service brake 8 is applied or simultaneously therewith. The kineticenergy, which is still driving the vehicle 1 in the coasting operation,is thereby not simply only converted to heat but is converted by theelectric motor 3 in the generator operation to electric energy, which isstored in the battery 7 and will be available again as a driving torque21′ for further driving of the electric motor 3. As soon as the vehicle1 is stationary or is stationary for a previously definable period oftime, the parking brake 10, controlled by way of the hybrid drivecontrol unit 12, the bus 17 and the parking brake control unit 13, isautomatically locked.

In the case of a starting prompt, for example, at a traffic light infront of which the vehicle 1 is stopped, the locked parking brake 10 isautomatically released and the vehicle 1 is started by the electricmotor 3. For this purpose, the accelerator pedal and the service brakepedal 9 are monitored and their conditions are evaluated. For example,when the service brake pedal 9 is released and the accelerator pedal isoperated, the starting operation will take place. By way of the trailerbrake valve 19, a trailer brake is simultaneously opened. The electricmotor 3 assists the starting by its driving torque 21′ in addition tothe driving torque 21 of the internal-combustion engine 2. If the latterhas been switched off, the electric motor 3, by means of engaging theclutch 4, can start the internal-combustion engine 2 immediately orafter the expiration of a previously definable time period.

FIG. 3 is a simplified schematic graphic view of a start-stop operationwith a use range 30. A torque M is entered above a rotational speed n ofthe hybrid drive. Above the abscissa, a driving operation is situated;below the abscissa, a charging operation is situated, similar to the oneshown in FIG. 2. The use range 30 of the start-stop operation issituated in the range of the starting rotational speeds starting at 0.In this use range 30, it is possible to advantageously utilize thesynergies of the automatically controlled parking brake 10 in connectionwith the hybrid drive, in order to lower the fuel consumption, increasethe driving comfort and the safety and lower the wear.

Referring to FIG. 4, an exemplary process is disclosed by theillustrated flow chart. After starting, the process determines, monitorsand analyzes performance parameters of the vehicle, of theinternal-combustion engine, of the electric motor, of the service brakeand of the electric parking brake (S1). The performance parametersfeature the vehicle speed, the rotational wheel speed, the rotationalspeeds of the internal-combustion engine and of the electric motor,operations and conditions of a service brake pedal, of a parking brakepedal and of an accelerator pedal. Based on step S1, it is possible thatan emergency running function situation occurs (S2). Under normaloperation, the process automatically releases the electric parking brakein the case of a starting prompt because of determined performanceparameters (S3). The process then drives the vehicle via the electricmotor for the start (S4). The process starts the internal-combustionengine by way of the electric motor if the internal-combustion engine isswitched off (S5). The process drives the vehicle by way of the electricmotor and the internal-combustion engine (S6). The process activates agenerator operation of the electric motor in the case of a brakingprompt because of determined performance parameters (S7). The processactivates the service brake (S8). The process automatically locks theelectric parking brake when the vehicle is stopped after a previouslydefinable deceleration time (S9) before ending.

FIG. 4 illustrates a first emergency running function situation when acircuit defect of the service brake is determined and, when the vehicleis driving, a braking prompt takes place via the service brake pedaland/or the parking brake lever. In that emergency running situation, theprocess activates a generator operation of the electric motor (S10). Theprocess activates the electric parking brake (S11). The processautomatically locks the electric parking brake when the vehicle isstopped after a previously definable deceleration time (S12).

In addition, emergency running functions, such as a so-called “secondarybraking I and II”, are contemplated. In the case of defects of a brakecircuit or of a service brake pedal 9, an assist by the parking brake 10is prompted. This can take place, for example, automatically or manually(after informing the driver, for example, by way of a display) by way ofthe parking brake lever 11. Then a stepped range of the electric motor 3in the generator operation is switched on by its control unit 16, inorder to assist the braking. The parking brake 10 can also be used in astepped manner controlled by its control unit 13, so that the vehicle 1,for example, in the event of a circuit defect determined by monitoringthe performance parameters, can nevertheless be braked.

When the vehicle 1 is stationary, as described above, an automaticlocking of the parking brake 10 takes place. A defective service brakepedal 9 can also be determined by monitoring the performance parameters.In this case, for example, intact units of the control unit ABS 14 areactivated, which have a compressed-air storage tank connection, and canelectromechanically control the compressed air for the braking. Abraking prompt can also take place in the driving condition by way ofthe parking brake lever 11, in which case the parking brake 10 isapplied in a stepped manner as described. A simultaneous activating ofthe electric motor 3 in the generator operation also takes place in thiscase. This generator operation can also be controlled in a steppedmanner. For this purpose, the performance parameters are also determinedand analyzed in order to correspondingly calculate and control assisttorques. When assisting this “secondary braking”, for example, thetrailer braking valve 19 is electrically or pneumatically excited tosynchronously brake the trailer 33 by way of the still intact thirdbrake circuit. Parallel thereto, by way of the bus 17, 18, an electricdeceleration request signal is transmitted to a trailer brake controlunit (not shown), so that the latter will pneumatically brake thetrailer in a synchronous manner.

It is, for example, further contemplated that, during a brakingoperation in the start-stop mode, engine braking functions of theinternal-combustion engine 2 are also utilized in that the generatortorque 25 is transmitted to the internal-combustion engine 2 by theclutch 4, which internal-combustion engine 2 is controlled by theinternal-combustion control unit 15 into a corresponding engine brakingoperation condition.

Braking prompts can also be carried out by so-called assist systems,such as a braking assist or a cruise control.

The computing operations, pertaining tables and algorithms may alreadybe present and utilized in the software—the existing control unitsand/or in the central computer. It is naturally also conceivable that anadditional control unit for the start-stop operation and the emergencyrunning functions is used separately.

TABLE OF REFERENCE SYMBOLS

-   -   1 Vehicle    -   2 Internal-combustion engine    -   3 Electric motor/generator    -   4,4′ Clutch    -   5 Transmission    -   6 Wheel    -   7 Battery    -   8 Service brake    -   9 Service brake pedal    -   10 Parking brake    -   11 Parking brake lever    -   12 Hybrid drive control unit    -   13 Parking brake control    -   14 ABS control unit    -   15 Internal-combustion engine control unit    -   16 Electric motor control unit    -   17 Bus    -   18 Trailer bus    -   19 Trailer brake valve    -   20 Trailer interface    -   21,21′ Driving torque    -   22 Starting torque    -   23 Service brake torque    -   24 Parking brake torque    -   25 Generator torque    -   26 Boosting performance    -   27 Storage capacity    -   28 Charging operation    -   29 Driving operation    -   30 Use range    -   31 Charging current    -   32 Driving current    -   33 Trailer    -   34 Actuator    -   MV Minimal consumption    -   SSB Start-stop range

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

1. A vehicle, comprising: a hybrid drive having an internal-combustionengine and an electric motor; a service brake with an ABS control unitand a service brake pedal; an electric parking brake with a parkingbrake control and a parking brake lever; at least one clutch forcoupling the internal-combustion engine and the electric motor withwheels of the vehicle; a hybrid drive control unit for controlling thehybrid drive; and a bus for connecting control units, actuators andsensors of the vehicle and for transmission of control signals; whereinthe electric parking brake is connected with the hybrid drive controlunit for an automatic controllability in previously definable operatingconditions of the vehicle.
 2. The vehicle according to claim 1, whereinthe electric parking brake is equipped with an actuator constructed asat least one of a spring-type servo-cylinder, electromotive actuator,and electromechanical actuator.
 3. The vehicle according to claim 1,wherein the electric parking brake has a stepping capability withpreviously definable steps.
 4. The vehicle according to claim 3, whereina pulse width modulation of a triggering of the electric parking brakeis provided in the range of the stepping capability.
 5. The vehicleaccording to claim 1, wherein the electric parking brake has a bistablebehavior in a parked condition, whereby, when an electric supply fails,the electric parking brake is locked or released corresponding to apredetermination by the hybrid drive control unit or a driver'sintention.
 6. The vehicle according to claim 1, wherein the previouslydefinable operating conditions of the vehicle are at least one of astart-stop operation, an emergency running function in an event of acircuit defect of the service brake, and an emergency running functionin an event of a defective service brake pedal.
 7. The vehicle accordingto claim 1, wherein the internal-combustion engine is a diesel engine.